I am having an issue with the PHP mail.

It's working (finally) but only after searching through dozens of sites for clues.
This line does NOT work:


But this line does:


If I don't use the "@" the app doesn't return an error - and doesn't send any message or mail.

Is the "@" necessary because I'm on a Linux server?
And why is there no mention of this peculiarity anywhere in the manual?